Needle assemblies are used in different medical instruments in connection with a wide array of medical procedures. It is desirable for the needle assembly to be constructed in a way that minimizes the potential for a user such as a healthcare worker to come in contact with the cannula of the used needle assembly. One known type of arrangement for addressing this concern involves the use of a rigid cylindrical cap which is positioned over the cannula and engages the hub to which the cannula is connected. During use, the cylindrical cap is removed to expose the cannula. After using the syringe/needle assembly for its intended procedure, the cylindrical cap must be once again mounted on the hub to cover the used cannula. Oftentimes, the healthcare professional tries to replace the cylindrical cap on the needle assembly (e.g., in connection with a syringe) by “scooping” the cylindrical cap with the needle assembly. This may not be an easy or effective technique for repositioning the protective cap on the syringe/needle assembly. The cap can also become accidentally dislodged from the needle assembly, thus exposing the used cannula and presenting a potential danger.
Another proposal presented in U.S. Pat. No. RE 37,110 involves the use of a housing pivotally connected to a base which is associated with the needle assembly. The housing is adapted to be pivoted to a covering position in which the housing covers the cannula. In addition, a locking mechanism is provided between the housing and the base to lock the housing in the covering position relative to the cannula.
U.S. Pat. No. 5,662,617 discloses other proposals, some of which involve a sheath pivotally connected to a needle hub mount that is adapted to be mounted on a needle hub. In one disclosed embodiment, the side walls of the sheath are adapted to engage riblets on the needle hub when the sheath is pivoted toward the cannula. The engagement between the sheath side walls and the riblets on the needle hub is releasable to permit repeated releasable closure of the sheath.